AD & DNS: RODC not appear as Name Server?

Why ONLY the writable domain controller (RWDC) appear as “Name Server” in the DNS?

Why Read-only domain controller appears as “Host(A)” in the DNS?

*Note: This is a normal behavior

Reference:

https://social.technet.microsoft.com/wiki/contents/articles/4031.how-read-only-domain-controllers-and-dns-works.aspx

https://awinish.wordpress.com/2011/10/04/rodc-read-only-domain-controller/

https://technet.microsoft.com/en-us/library/cc754956(v=ws.10).aspx